1. David Toback Searching for New Particles at the Fermilab Tevatron 1 Search for New Particles at the Fermilab Tevatron Abstract Since the discovery of the top quark, there have been a number of exciting hints for new particles beyond the Standard Model of particle physics from the Fermilab Tevatron. In this talk I will present what I believe are some of the most tantalizing hints (e.g. one observed proton anti- proton collision appears so unlikely to be from known sources that of the 3 trillion collisions we observed, we expected 10 -6 ) and present the results of a recently finished systematic set of model independent searches using the novel Sleuth method to look for other hints. In addition, I will present some very preliminary results from the new Tevatron data and present prospects for a future upgrade which will make us even more sensitive and robust for future observations.

2. David Toback Searching for New Particles at the Fermilab Tevatron 2 Dave Toback Texas A&M University Department Colloquium September, 2002

3. David Toback Searching for New Particles at the Fermilab Tevatron 3 Overview Since the discovery of the 6 th and final(?) quark at the Fermilab Tevatron, the field of particle physics continues to progress rapidly During that data taking run, and since, there continue to be a number of exciting hints from Fermilab that there are new fundamental particles just around the corner waiting to be discovered This talk describes following up on some of what may be some of the best experimental hints

4. David Toback Searching for New Particles at the Fermilab Tevatron 4 Outline Overview: Fermilab and looking for new particles A hint?: An unusual event Model Independent Search Methods and Results: “Cousins,” Signature Based Searches and Sleuth The present and future: Taking more data and improving search robustness Conclusions

5. David Toback Searching for New Particles at the Fermilab Tevatron 5 The Known Particles Why do we need so many different particles? Why are some so much heavier than the others? How do we know we aren’t missing any? The Standard Model of particle physics has been enormously successful But:

6. David Toback Searching for New Particles at the Fermilab Tevatron 6 How to attack the problem Theorists: Theoretical Models Experimenters: Experimental Results Unexplained Phenomena Theoretical Parameters to Measure Results of Particle Searches and Parameter Measurements New Particles to Look For

7. David Toback Searching for New Particles at the Fermilab Tevatron 7 Fermi National Accelerator Laboratory (Fermilab Tevatron) The worlds highest energy experiment Proton Anti-Proton Collisions Center of Mass energy of 1.8 TeV 1 collision every 3.5  sec (300,000/sec) The data presented today corresponds to the study of ~5 trillion  pp collisions _P_P P

8. David Toback Searching for New Particles at the Fermilab Tevatron 8 Big Toys: The CDF and DØ Detectors Surround the collision point with a detector Beam Direction Collision point Two of the ~600 people now on the experiments

9. David Toback Searching for New Particles at the Fermilab Tevatron 9 Review: How does one search for new particles at the Tevatron? Look at the final state particles from the  pp collision (an event) We know what Standard Model events look like Look for events which are “Un-Standard Model Like”

10. David Toback Searching for New Particles at the Fermilab Tevatron 10 Example Final States: Two Photons and Supersymmetry _P_P P _P_P P Supersymmetry: Standard Model:  +Supersymmetric Particles in Final State  No Supersymmetric Particles in Final State

11. David Toback Searching for New Particles at the Fermilab Tevatron 11 Look at collisions with Two Final State Photons SUSY particles would leave the detector (not interact) Use Conservation of Momentum and “observe” the missing momentum/energy Look for Gravitinos or Neutralinos this way Note: A number of other models also predict final states with  “Other Stuff” _P_P P

12. David Toback Searching for New Particles at the Fermilab Tevatron 12 Search for anomalous  events at CDF Example of what might show up: Supersymmetry would show up as an excess of events with large Missing Energy Our observations are consistent with background expectations with one possible exception -Low Energy  -Large # of Background Events -High Energy  sub-sample -Smaller # of Background Events Missing Energy Events Missing Energy * R. Culbertson, H. Frisch, D. Toback + CDF PRL 81, 1791 (1998), PRD 59, 092002 (1999 )

13. David Toback Searching for New Particles at the Fermilab Tevatron 13 The interesting event on the tail In addition to  +Missing Energy this (famous) event has two high energy electron candidates –e candidate passes all standard ID cuts, but there is evidence which points away from the e hypothesis. We may never know. Very unusual Good example of getting an answer which is far more interesting than what you asked for How unusual? Particle Physics Jargon: Energy imbalance=Missing Energy=E T -=MET

14. David Toback Searching for New Particles at the Fermilab Tevatron 14 Predicted by the Standard Model? Dominant Standard Model Source for this type of event: WW  –WW    e  e    ee    8x10 -7 Events All other sources (mostly detector mis- identification): 5x10 -7 Events Total: (1 ± 1) x 10 -6 Events Perspective: Look at 5 trillion collisions, expect 10 -6 events with two electrons, two photons and an energy imbalance

15. David Toback Searching for New Particles at the Fermilab Tevatron 15 So what is it? Is it SUSY? Statistical fluctuation? New physics? We’ve been looking for Supersymmetry and the Higgs for a long time. Is it either of those? –No model of Higgs I know about predicts this type of event –Could be Supersymmetry –Technicolor? –Others? _P_P P

16. David Toback Searching for New Particles at the Fermilab Tevatron 16 Supersymmetry This event looks like a natural prediction of the model. (Well…after it was seen by the theoretical community) However: –However, most models predict additional events with  +Missing Energy. We don’t see those –Also, no others seen by the Tevatron or LEP

17. David Toback Searching for New Particles at the Fermilab Tevatron 17 What to do? Our anomaly doesn’t look like the currently favored models of Supersymmetry or the Higgs While there are other models which predict this event most have fallen by the wayside, or also predict the same final state of  +Missing Energy. Perhaps there is something far more interesting and unpredicted going on! But what? Need more hints…

18. David Toback Searching for New Particles at the Fermilab Tevatron 18 Outline A survey of the follow up on what may be some of the best hints in particle physics Overview: Fermilab and looking for new particles A hint?: An unusual event Model Independent Search Methods and Results: “Cousins,” Signature Based Searches and Sleuth The present and future: Taking more data and improving search robustness Conclusions

19. David Toback Searching for New Particles at the Fermilab Tevatron 19 What to do? As experimentalists we decided to do two things: 1.Investigate the predictions of models which predict this type of even No results which followed up on the model predictions yielded additional hints 2.Need to do something new and not based on existing models

20. David Toback Searching for New Particles at the Fermilab Tevatron 20 Model Independent Search Need a new method Use properties of the event to suggest a more model independent search Look for “Cousins” of our events –I.e., Others with “similar” properties –Others of this ‘type’ In some sense we are looking for many models all at once (At the time this was a non-standard method of looking for new particles)

21. David Toback Searching for New Particles at the Fermilab Tevatron 21 Unknown Interactions: Example _P_P P Unknown Interaction _P_P P Similar Unknown Interaction Other final state particles Anything These two events would be Cousins

22. David Toback Searching for New Particles at the Fermilab Tevatron 22 Example of a “Cousin” Search A priori the ee  event is unlikely to be Standard Model WW  production –(~10 -6 Events) Guess that the unknown interaction is “Anomalous” WW  production and decay Look for similar unknown interaction with –WW  (qq)(qq)  jjjj –Br(WW  jjjj) >> Br(WW  ee+MET) By branching ratio arguments: Given 1  +ll+MET event  Expect ~30  jjj “Cousin” events Technicolor models predict this type of signature

23. David Toback Searching for New Particles at the Fermilab Tevatron 23  + Jets Search at CDF Look in  data to for anomalous production of associated jets from quark decays of W’s No Excess ~30 Event excess would show up here -Low Energy  -Large # of Background Events -Higher energy  sub-sample -Smaller # of Background Events Number of Jets * R. Culbertson, H. Frisch, D. Toback + CDF PRL 81, 1791 (1998), PRD 59, 092002 (1999 )

24. David Toback Searching for New Particles at the Fermilab Tevatron 24 Generalize: Signature Based Search Generalize the Cousin Search to a full Signature Based Search Search for an excess of events in the  X final state, where X is –Gauge Boson W, Z, gluon (  jet) or extra  –Quarks Light quarks (up, down, strange or charm  jet) b-quarks (jet with long lifetime) t-quarks (t  Wb) –Leptons Electrons, muons, taus and neutrinos Leptons from W  l, Z  ll or Z  No rate predictions for new physics, just look for an excess

25. David Toback Searching for New Particles at the Fermilab Tevatron 25  +X Signature Based Search Results CDF Run I All results are consistent with the Standard Model background expectations with no other exceptions High Acceptance, Large # of Background Events Lower Acceptance, Smaller # of Background Events * R. Culbertson, H. Frisch, D. Toback + CDF PRL 81, 1791 (1998), PRD 59, 092002 (1999 )

26. David Toback Searching for New Particles at the Fermilab Tevatron 26 Well…Maybe….  jj Another event in the data with similar properties Not part of the “official”  dataset No significant Missing Energy, but the energy resolution isn’t as good Not quite as interesting. Background only at the 10 -4 level Again, no good Standard Model explanation     j j More Particle Physics Jargon j=jet: Usually from a final state quark or gluon

27. David Toback Searching for New Particles at the Fermilab Tevatron 27 Another Cousins Search _P_P P Unknown Interaction _P_P P Similar Unknown Interaction Other final state particles Anything

28. David Toback Searching for New Particles at the Fermilab Tevatron 28 Lepton+Photon Cousin search Finds the ee  +Met and mm  jj events All the other channels agree with background expectations except  +Met: 11 events on a background of 4.2±0.5 No excess in e  +Met!?! 5 on a background of 3.4±0.3 Not statistically significant enough to be a discovery, but appears quite similar to other anomalies in that the events combines leptons, photons and Missing Energy No other events look all that unusual * J. Berryhill, H. Frisch, D. Toback + CDF PRL 89, 041802(2002), PRD 66, 012004 (2002)

29. David Toback Searching for New Particles at the Fermilab Tevatron 29 What to do…. Not clear what to make of this excess Standard Model W  can produce this via W      +Met Anomalous W  production? But why is there no excess in e  +Met Really need more data! However, we are encouraged that this new model independent method gave us a new hint. Take the next step: Expand this search in a larger, systematic and more a priori way to find other hints unpredicted by theory. Look at DØ data.

30. David Toback Searching for New Particles at the Fermilab Tevatron 30 Sleuth B. Knuteson, D. Toback + DØ PRD 62, 092004 (2000) A friend to help us systematically look in our data for experimental clues in model independent ways

31. David Toback Searching for New Particles at the Fermilab Tevatron 31 A New Model-Independent Search Method: Sleuth Assume nothing about the new particles except that they are high mass/E T –If it were low mass, we most likely would have seen it already Systematically look at events by their final state particles: Signature Based Search Search for new physics by looking for excesses in multi-dimensional data distributions

32. David Toback Searching for New Particles at the Fermilab Tevatron 32 Sleuth Algorithm A priori search prescription to define which regions you can look in to maximize sensitivity Find most interesting region (largest excess relative to backgrounds) Run hypothetical similar experiments using background expectations and systematic errors Measure of interestingness: Fraction of hypothetical similar experiments (from backgrounds alone) which have an excess more significant than the one observed Background expectation Example signal events E T of X E T of Y

33. David Toback Searching for New Particles at the Fermilab Tevatron 33 How well does Sleuth work? Example: Both WW and top quark pair production are good examples of high E T events which might show up at DØ with Sleuth if we didn’t know about them Run Mock Experiments pretending we don’t know about WW and  tt production to see if we can find it. Also look in samples with nothing new and interesting 4 Example Samples: –e  + 0 Jets WW –e  + 1 Jet –e  + 2 Jets  tt –e  + 3 Jets Lots of other examples in other channels as well including Supersymmetry, Leptoquarks etc.

34. David Toback Searching for New Particles at the Fermilab Tevatron 34 Test Results:  tt and WW as unknowns ~50% of experiments would give a >2  excess in at least one channel Significance of excess in standard deviations (All overflows in last bin) Mock Experiments Bkg only Bkg +WW +  tt % of Mock Experiments Expectations Remember: The top quark discovery required combining MANY different channels and this is just one

35. David Toback Searching for New Particles at the Fermilab Tevatron 35 Test Results:  tt and WW as unknowns Predict that ~50% of experiments would give a >2  excess. What about our data? B. Knuteson, D. Toback + DØ PRD 62, 092004 (2000) Excesses corresponding to WW and  tt found even though Sleuth didn’t know what it was looking for //////// Run I DØ Data

36. David Toback Searching for New Particles at the Fermilab Tevatron 36 Sleuth cont…. Sleuth shows that when there is no signal to be observed, it doesn’t predict one When there is a significant signal to be observed, even if we didn’t know where to look, Sleuth has a good chance of finding it Now that we have a powerful tool, apply it to lots of different data sets from Run I

37. David Toback Searching for New Particles at the Fermilab Tevatron 37 Sleuth on Run I Data at DØ Run Sleuth on many sets of DØ data in addition to the photon final states in the hopes of finding an unexpected new hint e  + X W+Jets “like” Z+Jets “like” (l/  ) (l/  ) (l/  ) B. Knuteson, D. Toback + DØ PRL 86, 3712 (2001), PRD 64, 012004 (2001) Nothing New

38. David Toback Searching for New Particles at the Fermilab Tevatron 38 Final Run I Results: DØ Looked at over 40 final states Plot the significance of every result in terms of standard deviations No signature has a significant excess Significance (in  ) of the most anomalous region in a dataset Each entry in the histogram is a different final state

39. David Toback Searching for New Particles at the Fermilab Tevatron 39 Summarizing the Sleuth Results The most anomalous data set at DØ (according to Sleuth) is ee+4jets; excess is 1.7  However, since we looked at so many places, expected this large an excess. Bottom line: Nothing new Significance (in  ) of most anomalous dataset taking into account the number of places looked Significance (in  ) of the most anomalous dataset as a standalone result DØ Run I Data If we had an ensemble of Run I data sets, would expect 89% of them would give a larger “excess”

40. David Toback Searching for New Particles at the Fermilab Tevatron 40 Sleuth and the CDF anomalies Sleuth certainly finds the CDF anomalies already described to be highly unlikely to be statistical fluctuations when compared to known backgrounds However, it can’t have anything to say about whether we forgot a background or an unknown set of detector malfunctions Bottom line: Sleuth doesn’t (can’t) have anything to say about whether the CDF anomalies are real. It doesn’t see any similar anomalies, or new anomalies in DØ

41. David Toback Searching for New Particles at the Fermilab Tevatron 41 Outline A survey of the follow up on what may be some of the best hints in particle physics Overview: Fermilab and looking for new particles A hint?: An unusual event Model Independent Search Methods and Results: “Cousins,” Signature Based Searches and Sleuth The present and future: Taking more data and improving search robustness Conclusions

42. David Toback Searching for New Particles at the Fermilab Tevatron 42 Run II of the Tevatron Finally taking more data!!! Collision Energy: 1.8 TeV  2.0 TeV 1 collision every 396 nsec Upgraded detectors Better acceptance, more data more quickly Started taking new data –20 times the data by the end of 2005 –200 times the data by the end of 2009

43. David Toback Searching for New Particles at the Fermilab Tevatron 43 A new CDF Run IIa Event Candidate Two photons, one electron and Missing Energy Preliminary background estimate at the 3x10 -3 level Clearly similar to the other CDF anomalies Preliminary confidential result

44. David Toback Searching for New Particles at the Fermilab Tevatron 44 Hmmm… It’s very encouraging to see this new event. But we’re still left with nagging doubts on our hints: Only single (unrelated?) anomalous events and a 2  excess Events with photons and missing energy continue to be a common theme…  However, “Only at CDF” also seems to be a common theme… Any differences between CDF and DØ that might explain this? Perhaps. The DØ has a “pointing calorimeter” which gives more confidence that photons are from the collision point. CDF does not.

45. David Toback Searching for New Particles at the Fermilab Tevatron 45 So what? Cosmic rays can interact with the CDF detector and produce an additional fake photon with corresponding energy imbalance Could the photons in these anomalous events be from cosmic rays on top of an already complicated collision? We searched the events for any reason to believe that this might be causing the problem. We found no evidence that this was the case The rate for this as a background is tiny

46. David Toback Searching for New Particles at the Fermilab Tevatron 46 Prompt Photons Cosmic Rays Powerful Tool: Time of arrival What we’d really like is a tell-tale affirmative handle that would put this to bed once and for all at CDF… Look at the time the photons “arrives” at the detector and compare with the expected time of flight from the collision point Cosmics are clearly separated from real events

47. David Toback Searching for New Particles at the Fermilab Tevatron 47 The down side Only indirect measurements available in Run I: Very inefficient at low energies The whole detector isn’t instrumented (e.g. no possibility of timing for second electron candidate) Run I inefficiency

48. David Toback Searching for New Particles at the Fermilab Tevatron 48 Run IIa at CDF Expected only 1.4 of the 3 e/  objects in the ee  +Met event to have timing info: Saw 2 Same for the e  +Met event Only half of events in the  +Met sample have timing information While we’ve expanded the coverage of the timing system in Run IIa, it still has the same lousy efficiency.

49. David Toback Searching for New Particles at the Fermilab Tevatron 49 An upgrade to CDF: EMTiming To solve these problems, we are adding a direct timing measurement of the photons in the electromagnetic calorimeters to the CDF detector ~100% efficient for all photons of useful energy –Could get timing for all objects in any new ee  +Met events –~5% effic  ~100% effic Old New

50. David Toback Searching for New Particles at the Fermilab Tevatron 50 In addition to confirming that all photons are part of the collision, this would reduce the backgrounds for certain types of high profile searches with photons and MET SUSY (N 2   N 1, light gravitinos) Large Extra Dimensions Excited leptons New dynamics (like Technicolor) V+Higgs  V+  W/Z+  production Whatever produced the ee  MET candidate event Whatever produced the CDF  +Met excess Direct Physics Benefits

51. David Toback Searching for New Particles at the Fermilab Tevatron 51 How do we do it? Electronic design is actually quite simple and similar systems already exist on the detector Take photo-tube signal and put it into a TDC and readout Large system to add to existing (very large) detector

52. David Toback Searching for New Particles at the Fermilab Tevatron 52 To set the scale: adding cabling and readout electronics for about 2000 phototubes at CDF Large international collaboration led by TAMU (other institutions such as INFN-Frascati, Univ. of Chicago, Univ. of Michigan, Fermilab and Argonne are contributing components and funding) ~$1M project including parts and labor –Project fully approved by CDF –Italian funding fully approved (buys some of the components) –Fermilab PAC Stage 1 project approval –Positive feedback from U.S. DOE (project funding review yesterday). Remaining funding is expected by November –TAMU funding approved by U.S. DOE About the project

53. David Toback Searching for New Particles at the Fermilab Tevatron 53 Making the Future Successful For Run II we have/need: More data. (Taking it as we speak…) Powerful targeted searches for Supersymmetry and the Higgs New search strategies like Sleuth: –While it can’t be as sensitive as a dedicated search, it may be our only shot if we guess wrong about where to look in our data in the future. –A natural complement to the standard searches Working on tools to make any potential discovery more robust

54. David Toback Searching for New Particles at the Fermilab Tevatron 54 Conclusions The Fermilab Tevatron continues to be an exciting place to search for new particles There have been a number of interesting hints in the data with photons and we’ve worked hard to follow up on them We are well poised to make a major discovery in Run II

55. David Toback Searching for New Particles at the Fermilab Tevatron 55

56. David Toback Searching for New Particles at the Fermilab Tevatron 56 Run I Timing: Problems Cosmic rays, know for sure that the final state particles are part of the event (Robustness) Run IIa Timing Preliminary results Run IIb EMTiming: Why? –Design –Estimated results: gg+Met, LED, Zgamma (order?) Conclusions: –Interesting events to follow up on –Have the technology to deal with unexpected events from an analysis point of view –Need more data (that’s coming!!!) –Need better tools to confirm the robustness of the results.

57. David Toback Searching for New Particles at the Fermilab Tevatron 57 Run IIa at CDF Expected only 1.4 of the 3 e/  objects in the ee  +Met event to have timing info: Saw 2 Same for the e  +Met event Only half of events in the  +Met sample have timing information While we’ve expanded the coverage of the timing system in Run IIa, it still has the same lousy efficiency. –E.g. Only ~5% of ee  +Met events would have timing for all 4 objects

58. David Toback Searching for New Particles at the Fermilab Tevatron 58 The plan for the next few years Next two years: Pursue best guesses for Run II –Dedicated searches (Fermilab’s top priority) Higgs Boson, Supersymmetry –Signature based “cousins” and Sleuth searches Lepton + Photon + X, Photon+Photon +X, Photon+Met+X –Gain full funding for EMTiming project and build Next five years: Pursue best hints from Run II –Higgs signal? Supersymmetry? Twenty ee  MET events? –Some other completely unexpected events? –Install the EMTiming upgrade and take data

59. David Toback Searching for New Particles at the Fermilab Tevatron 59 Some thoughts on Sleuth Sleuth is sensitive to finding new physics when it is there to be found Would find events like the ee  +MET naturally Would be sensitive to many SUSY and Higgs signatures While it can’t be as sensitive as a dedicated search, it may be our only shot if we guess wrong about where to look in our data in the future A natural complement to the standard searches

60. David Toback Searching for New Particles at the Fermilab Tevatron 60 Cosmic Ray backgrounds at CDF Problem: Cosmic rays enter the detector and fake a photon (+Met) Question: Can’t you just get rid of the cosmic ray backgrounds? Answer: Photons from the primary event, and photons from cosmic rays look very similar in the CDF calorimeter. Many are real photons. Points: Photons from Cosmics Solid: Photons from collisions

61. David Toback Searching for New Particles at the Fermilab Tevatron 61 Where are we and what’s next? It’s very encouraging to see this new event. But we’re still left with nagging doubts on our tantalizing hints: Only single (unrelated?) anomalous events and a 2  excess There is some evidence that one of the electrons in the ee  +MET event is a fake –After extensive study it’s not clear what that object is (we may never know) –We’ve entirely replaced that calorimeter for Run II

62. David Toback Searching for New Particles at the Fermilab Tevatron 62 This event was different than what we were looking for How many did we expect from background? This is a difficult question Can’t estimate the probability of a single event (measure zero) “How many events of this ‘type’ did we expect to observe in our data set from known Standard Model sources?” Try to define a “reasonable” set of criteria to define ‘type’ after the fact

63. David Toback Searching for New Particles at the Fermilab Tevatron 63 Overview of Sleuth Define final state signatures –(which particles in the final state) A priori prescription for defining search parameters and regions in those variables A systematic look for regions with an excess (more events than expected) with large Energy Find most interesting region Compare with the expectations from hypothetical similar experiments using background expectations Take into account the statistics of the large number of regions searched and systematics of the uncertainties of the backgrounds

64. David Toback Searching for New Particles at the Fermilab Tevatron 64 So where are we? We have one very interesting event Statistically unlikely to be from known Standard Model backgrounds No Cousins in the  +X final state What’s next?

65. David Toback Searching for New Particles at the Fermilab Tevatron 65 Take more data!!! However…

66. David Toback Searching for New Particles at the Fermilab Tevatron 66 Don’t want to get caught unprepared again Having to estimate the background for an interesting event a posteriori is not good Need a systematic way of finding more interesting events Need a more systematic plan of what to do when we find them Need a systematic way of estimating the significance of unexpected events

67. David Toback Searching for New Particles at the Fermilab Tevatron 67 Towards a model independent solution Many believe Supersymmetry is correct, but what if we haven’t gotten the details right and we’re just looking at the wrong final states –Looking for photons in the final state in 1994 was not even considered as a Supersymmetry discovery channel Ought to be better prepared to search for new physics when we don’t know what we are looking for Design a system which should also find the kinds of things we know to look for

68. David Toback Searching for New Particles at the Fermilab Tevatron 68 The Fermilab Accelerator ~4 Miles in Circumference

69. David Toback Searching for New Particles at the Fermilab Tevatron 69 Identifying the Final State Particles Many particles in the final state –Want to identify as many as possible –Determine the 4-momentum Two types: short lived and long lived –Long lived: electrons, muons, photons… –Short lived: quarks, W, Z…“decay” into long lived particles Observe how long lived particles interact with matter –Detection

70. David Toback Searching for New Particles at the Fermilab Tevatron 70 mesons etc. In the Detector The qq pairs pop from the vacuum creating a spray of particles Short Lived Particles in the Detector _P_P P Jet

71. David Toback Searching for New Particles at the Fermilab Tevatron 71 Long Lived Particles in the Detector e  jet  Long lived Supersymmetric particles do not interact in the detector Very much like neutrinos Beam Axis Tracking Chamber EM Layers Hadronic Layers Steel/Iron Calorimeter Muon Chamber

72. David Toback Searching for New Particles at the Fermilab Tevatron 72 X Y e+e+ e-e- X Y e+e+ Event with energy imbalance in transverse plane Event with energy balance in transverse plane Energy in direction transverse to the beam: E T = E sin(  ) Missing E T : MET Event with MET

73. David Toback Searching for New Particles at the Fermilab Tevatron 73 An attractive theoretical solution One of the most promising theories is Supersymmetry which is an attempt to solve these (and other) problems Each Standard Model particle has a Supersymmetric partner

74. David Toback Searching for New Particles at the Fermilab Tevatron 74 Supersymmetric Particles? SM Particles Superpartners Other New Particles: Higgs Boson

75. David Toback Searching for New Particles at the Fermilab Tevatron 75 Predictions and Comparisons Supersymmetric Predictions Standard Model Predictions Select events above threshold or Look for excess of events with large MET 1 2 3 1 2 3 123 Background above threshold X MET Photon E T

76. David Toback Searching for New Particles at the Fermilab Tevatron 76 Example with Supersymmetry –Background Expectations from Standard Model –How the data might look Prediction from Supersymmetry Look for Regions where the backgrounds are small and the predictions for Supersymmetry are large

77. David Toback Searching for New Particles at the Fermilab Tevatron 77 How we might observe evidence of Supersymmetry in a laboratory Example* Final State: Two electrons, two photons and two Gravitinos *Gauge Mediated Supersymmetry Breaking _P_P P Proton Anti-Proton Collision (Actually the quarks inside)

78. David Toback Searching for New Particles at the Fermilab Tevatron 78 Look at collisions with Two Final State Photons _P_P P A number of other models also predict final states with  +“Other Stuff” Good reason to believe a sample of events with two high energy photons in the final state can be an unbiased sample in which to search for evidence of New Particles (Gravitinos? Neutralinos?) * Work done at University of Chicago with H. Frisch and R. Culbertson on CDF. Results published in PRL & PRD Leave detector causing an energy imbalance

79. David Toback Searching for New Particles at the Fermilab Tevatron 79 Typical Search for New Particles Look at the final state particles from a Proton Anti-Proton collision Use a computer (Monte Carlo) to simulate the interaction –Probability a collision might produce Supersymmetric particles –Properties of the final state particles Same for known Standard Model interactions which might produce similar results Compare

80. David Toback Searching for New Particles at the Fermilab Tevatron 80 Example Final States: Two Photons and Supersymmetry _P_P P _P_P P Supersymmetry:Standard Model:  +Supersymmetric Particles in Final State  No Supersymmetric Particles in Final State

81. David Toback Searching for New Particles at the Fermilab Tevatron 81 Set limits on one of the models Since counting experiment is consistent with expectations we set limits on the new physics production at the 95% Confidence Level This constrains/excludes some theoretical models Gives feedback to theoretical community Example Limit Example Theory Excluded this side Unexcluded this side Lightest Chargino Mass

82. David Toback Searching for New Particles at the Fermilab Tevatron 82 Quantitative Estimate Use a computer simulation of Standard Model WW  production and decay Use known W decay branching ratios and detector response to the various decays of W’s Result: Given 1  +ll+MET event  Expect ~30  jjj events

83. David Toback Searching for New Particles at the Fermilab Tevatron 83 Take more data The Fermilab Tevatron is being upgraded The detectors are being upgraded Already started taking data this year Should be able to answer the question with 20 times the data: –Scenario 1: We see more than a couple cousins Study the sample for more clues for its origins –Scenario 2: We see very few or none Most likely a fluctuation (of whatever it was).

84. David Toback Searching for New Particles at the Fermilab Tevatron 84 Labeling Final State Signatures Final State particles: –e, , j, b, c, MET, W or Z Each event is uniquely identified: –All events which contain the same number of each of these objects belong to the same final state

85. David Toback Searching for New Particles at the Fermilab Tevatron 85 Using Sleuth on Run I Data Look in events with an electron and a muon for a excess which might indicate a new heavy particle(s) Why e  ? (why not?) –Lots of theory models –Supersymmetry? Anomalous Top quarks? Backgrounds include good example of heavy particles to look for –Top quarks, W bosons

86. David Toback Searching for New Particles at the Fermilab Tevatron 86  tt and WW production _P_P P _P_P P e  + 0 Jets e  + 2 Jets  High E T relative to other backgrounds

87. David Toback Searching for New Particles at the Fermilab Tevatron 87 Fraction of hypothetical similar experiments (from backgrounds alone) which have an excess more significant than the one observed Mock data with no signal Probability is flat as expected e  + 1 Jetse  + 0 Jets e  + 3 Jetse  + 2 Jets Small P is interesting Smallest bin is <5% No indication of anything interesting

88. David Toback Searching for New Particles at the Fermilab Tevatron 88 Sleuth with WW and  tt e  + 1 Jets e  + 0 Jets e  + 3 Jets e  + 2 Jets Pretend we don’t know about WW and  tt Mock experiments with WW and  tt as part of the sample Observe an excess in 0 Jets (WW production) 2 Jets (tt production) in the mock trials Remember: Small P is interesting Smallest bin is <5%

89. David Toback Searching for New Particles at the Fermilab Tevatron 89 Sleuth  tt Include WW as a background Expect an excess in 2 Jets only  tt production e  + 1 Jetse  + 0 Jets e  + 3 Jetse  + 2 Jets

90. David Toback Searching for New Particles at the Fermilab Tevatron 90 Finding  tt alone All overflows in last bin Significance of excess in standard deviations Excess corresponding to  tt Use all backgrounds except  tt and look for excesses //////// Mock Experiments Bkg only Bkg +  tt

91. David Toback Searching for New Particles at the Fermilab Tevatron 91 The e  X Sleuth Results We see no evidence for new physics at high P T in the e  X data Use all backgrounds and look for excesses ////////

92. David Toback Searching for New Particles at the Fermilab Tevatron 92 Warning: If you are looking for an overview and/or current status of the important theoretical models we’re looking for at the Tevatron, you’ve come to the wrong talk. I won’t spend much time interpreting my results in terms of how they restrict the currently favored models. I don’t have much to say about prospects for Higgs or Supersymmetry at the Tevatron; same thing If you’ve come to hear about latest results from the Tevatron, I’m afraid I don’t have much to show.

93. David Toback Searching for New Particles at the Fermilab Tevatron 93 General rule for picking variables Looking for new high mass particles Mass-Energy Relationship –Decay to known Standard Model particles light in comparison –High energy long lived particles in final state High Mass  High E T Look at E T of the final state particles

94. David Toback Searching for New Particles at the Fermilab Tevatron 94 The EMTiming Project Dave Toback Texas A&M University (for the CDF Collaboration)

95. David Toback Searching for New Particles at the Fermilab Tevatron 95 Why do we need EMTiming? Two primary reasons to add timing to the EM Calorimeter: 1.Reduces cosmic ray background sources: Improved sensitivity for high-P T physics such as SUSY, LED, Anomalous Couplings etc. which produce  +Met in the detector 2.Provide a vitally important handle that could confirm or deny that all the photons in unusual events (e.g. CDF ee  +Met candidate event) are from the primary collision.

96. David Toback Searching for New Particles at the Fermilab Tevatron 96 Physics Motivation Types of high P T physics with photons and MET SUSY (N 2   N 1, light gravitinos) Large Extra Dimensions Excited leptons New dynamics V+Higgs  V+  W/Z+  production Whatever produced the ee  MET candidate event Whatever produced the CDF  +Met excess

97. David Toback Searching for New Particles at the Fermilab Tevatron 97 Cosmic Ray Backgrounds Example Problem: Backgrounds in photon+MET analysis dominated by cosmic rays in Run I at high E T. SUSY would also show up at high E T.

98. David Toback Searching for New Particles at the Fermilab Tevatron 98 Real photons vs. Cosmics Problem: Cosmic rays enter the detector and fake a photon (+Met) Question: Can’t you just make ID cuts and get rid of the cosmic ray backgrounds? Answer: Photons from the primary event, and photons from cosmic rays look very similar in the CDF calorimeter. Many are real photons. Points: Photons from Cosmics Solid: Photons from collisions

99. David Toback Searching for New Particles at the Fermilab Tevatron 99 Timing in the Calorimeter Run I showed that Timing in the Hadronic Calorimeter (HADTDC system) can help distinguish between photons produced promptly and from cosmic rays Prompt Photons Cosmic Rays

100. David Toback Searching for New Particles at the Fermilab Tevatron 100 Problem with HADTDC Timing An EM shower needs to leak into the hadronic section of the calorimeter to have timing  HADTDC system is very inefficient for low E T  Requiring timing for a photon gives a bias toward fake photons from jets In Run I: Expected ~1.4 of the 4 EM objects in ee  +Met to have timing. Only 2 did (both were in time) In Run IIa: Only ~5% of ee  +Met events would have timing for all objects. Run II  +MET Trigger threshold

101. David Toback Searching for New Particles at the Fermilab Tevatron 101 How EMTiming Would help Give timing for all useful photons at ~100% efficiency Z  Example SUSY Example

102. David Toback Searching for New Particles at the Fermilab Tevatron 102 More on how EMTiming Would help Example using known physics Z  : –Old system: Not fully efficiency until above 55 GeV –EMTiming: Use all events from the 25 GeV trigger Z  Example SUSY Example

103. David Toback Searching for New Particles at the Fermilab Tevatron 103 Improved Physics Sensitivity EMTiming would allow us to reduce the photon+MET E T thresholds. Factor of two cross section improvement

104. David Toback Searching for New Particles at the Fermilab Tevatron 104 Improved Confidence Convince us that all the clusters are from the primary collision Lepton+Photon excess in Run I: –25 GeV threshold, only ½ of the events have timing, lowering the threshold doesn’t add much  With EMTiming would, by reducing to 10 GeV photons, add a factor of 10 in timed-event rate. ee  +Met candidate events –5% of Run II events would have all EM cluster with timing. ýWith EMTiming would go to ~100% Robustness of discovery potential

105. David Toback Searching for New Particles at the Fermilab Tevatron 105 Hardware for EMTiming Project Add TDC readout to CEM and PEM Hardware is virtually identical to HADTDC system Small R&D costs Small technical risks

106. David Toback Searching for New Particles at the Fermilab Tevatron 106 Project Tasks and Hardware Add splitters to 960 CEM channels: –PEM bases already readout-ready Build more Transition boards/ASD’s –Space in crates on first floor already exists Recycle small-via TDC’s –Recycle crate and tracer, purchase new off the shelf power supply and processor Cables and connectors

107. David Toback Searching for New Particles at the Fermilab Tevatron 107 Splitters for the CEM CEM energy readout cards measure charge. Splitter is purely inductive so it doesn’t change the charge collected in any noticeable way. ~15% of voltage goes on the secondary to the ASD to fire the TDC Splitter Response at 40 GeV

108. David Toback Searching for New Particles at the Fermilab Tevatron 108 Splitter characteristics ASDs fire with 100% efficiency at high E T Timing resolution is 1.1nsec (1.0 from TDC) No evidence of TDC misfiring from noise No evidence of noise going to ADMEM’s

109. David Toback Searching for New Particles at the Fermilab Tevatron 109 Parts and Cost M&S costs for this project would be covered by outside sources/grants –Texas A&M (TAMU) –University of Chicago –INFN Will recycle much of the parts –Small-via TDC’s –PMT Base  Transition board cables (many connectors) –Spare crate and Tracer –Much of the PEM-Transition board connectors

110. David Toback Searching for New Particles at the Fermilab Tevatron 110 Assembly and Installation Responsibilities: Overall system, R&D, testing and readout: TAMU Splitters and cables: INFN, TAMU and UC w/FNAL technicians ASD and Transition boards: INFN TDC/Crates: TAMU and w/assistance from UM

111. David Toback Searching for New Particles at the Fermilab Tevatron 111 Activities before Run IIB Prior to Run IIb Shutdown –Finish R&D –Collect parts for cables and assemble (TAMU and FNAL) –Construct transition boards and ASD’s (INFN) –Assemble upstairs TDC crate (TAMU) –Test production components During RunIIb shutdown –Install PMT  Transition board cables –Install transition boards, ASD and dress cables –Install cables going upstairs –Test

112. David Toback Searching for New Particles at the Fermilab Tevatron 112 Summary EMTiming would significantly enhance searches for new high P T physics in photon final states EMTiming would give a vital handle indicating if high E T photons are from the primary collision in unusual events Small costs which are well understood –No hardware costs to FNAL –Significant percentage of cost is in recycled parts –Simply following existing designs Minimal R&D and technical risk

113. David Toback Searching for New Particles at the Fermilab Tevatron 113 Backup Slides

114. David Toback Searching for New Particles at the Fermilab Tevatron 114 How EMTiming Would help Give timing for all useful photons at ~100% efficiency Example using known physics Z  : –HADTDC: Not fully efficiency until above 55 GeV –EMTiming: Use all events from the 25 GeV trigger Z  Example SUSY Example

115. David Toback Searching for New Particles at the Fermilab Tevatron 115 Splitter Schematic Secondary Output : -0.15 x Input Signal shield primary Back of PCB Female LEMO Male LEMO primary shield 20 ’- 40 ’ of RG174 Primary Output primary shield Ferrite Male LEMO Front of PCB 5 Turns Input Signal 4 ” of RG174 Connects to original ADMEM line LEMO Connects to ASD transition board EMTiming Splitter

116. David Toback Searching for New Particles at the Fermilab Tevatron 116 Splitter Picture Female LEMO to ADMEM input (on back) Male LEMO to PMT anode Male LEMO to ASD transition board

117. David Toback Searching for New Particles at the Fermilab Tevatron 117 Splitter results at 10 GeV

118. David Toback Searching for New Particles at the Fermilab Tevatron 118 Run II e  +Met Candidate Two photons. One had timing, would have been nice to know if the other was from a cosmic or other beam related background…

119. David Toback Searching for New Particles at the Fermilab Tevatron 119 Other models results…

120. David Toback Searching for New Particles at the Fermilab Tevatron 120 Splitter Characteristics

121. David Toback Searching for New Particles at the Fermilab Tevatron 121 Splitter misfires in TDC system

122. David Toback Searching for New Particles at the Fermilab Tevatron 122 Benefits vs. Cost/Risk Benefits: Important improvements in acceptance and robustness for difficult photon searches Costs: Small project costs (<0.5% of Run IIb budget), no M&S outlay from FNAL Risks: Primary risk is currently the schedule. What if we don’t finish the installation on time? Modular design of system make it such that we can make the system exactly as it was before we installed; I.e., doesn’t affect the current readout. If we don’t finish on time, we will simply not hook up the system so we don’t affect the rest of the physics program.

123. David Toback Searching for New Particles at the Fermilab Tevatron 123 Parts, costs and who pays add Labor!!!!! Need this? Out of date… CEMParts & SparesTAMUChicagoINFNRecycledTotal Connectors~3000$18k PMT  TB Cable ~1000$3.5k Transition Board27$13.2k ASD27$40.5k ASD  TDC Cable 32$13.9k TDC7$33.6k Crate and Tracer1 & 1$10k Power Supply and Processor1 & 1$5k PEM Connectors~1000$9k PMT  TB Cable ~1000$2.9k$3.5k Transition Board18$8.9k ASD18$27k ASD  TDC Cable 20$8.7k TDC5$24k Total pre-Contingency costs$32k$22.6k$89.6k$76.7k$220.8k

124. David Toback Searching for New Particles at the Fermilab Tevatron 124

125. David Toback Searching for New Particles at the Fermilab Tevatron 125 Search for  events with large MET (Run I CDF Data) Supersymmetry would show up as an excess at large MET E T  >12 GeV, MET>35 GeV Expect 0.5±0.1 Events  Observe 1 Event E T  >25 GeV, MET>25 GeV Expect 0.5±0.1 Events  Observe 2 Events Our observations are consistent with background expectations with one possible exception. -High Acceptance -Large # of Background Events -Lower Acceptance -Smaller # of Background Events Energy Imbalance MET Events